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GeoAstro Applets

Chaos Game

Java

Miscel- laneous

	Enter latitude in decimal degrees, and press return key, enter longitude in decimal degrees, and press return key.
	enter gnomon height (meters), and press return key.
	Use the keys "y", "m", or "d" to increase the year, month, or day, or shift key and "y", "m", or "d" to decrease the year, month, or day.
	Use the command key and "u" or "d" to move up or down. Use "Reset" from the Details menu to reset the position and the zoom.
	enter aperture diameter (in mm), and press return key.
	is the year 2009
	Select "Write Data" or "Write Table" from the Details menu to open data windows.

Meridian line sundials were the earliest means of checking the accuracy of calendars. A special form was developed in Italy during the fifteenth century. Instead of using the shadow of an obelisk, the sun was allowed to shine through the wall or roof of a building onto a meridian line on the floor inside, and the point of light was used as the indicator. The diameter S of the disk of light is mainly determined by the apparent diameter α of the Sun: S = D·tan α The diameter a of the aperture and an amount due to diffraction (2·D·1.22·λ/a) has to be added to S.

Web Links

Santa Maria degli Angeli e dei Martiri (Wikipedia) A Guide to “The Sun in the Church” by J. L. Heilbron L'Almanacco Astronomico - La vostra eclisse Der Meridian im Dom von Mailand Churches as scientific instruments (J. L. Heilbron)

Books

J. L. Heilbron: The Sun in the Cathedral, Cathedrals as Solar Observatories, Harvard University Press, 1999. Marco Catamo, Cesare Lucarini: Il Cielo in Basilica. La Meridiana delle Basilica di Santa Maria degli Angeli e dei Martiri in Roma, A.R.P.A. Edizioni AGAMI, Roma 2002.